short cicuit data from client

[SELEC]

I am doing a short circuit study for a system. The fault level on 28KV side is, R1= 6.78727 OHM, X1=19.19640 Ohm.

On the SLD, it also shows that, R1(pu)=0.6787pu, X1(pu)=1.7196pu. 100MVA base

The above data doesn't make sense to me. The short circuit current derived from the above data.

 

[SELEC]

I just confirmed the data. The per unit data is right and the system source is very weak. From down sream, we have 40% loads are VFD controle, so I am really concerned about the harmonic distotion effect.

I am wondering if there is rule of thumb to calculate harmonic portion. or I have to run ETAP software.

 

[mpparent]

Check and see if the VFD's have filters.

Mike

 

[SELEC]

My lead told me that if we took out filters from VFD, VFD would be more expensive. That doesn't make sense to me.

 

[mpparent]

I'm certain that a filter in a VFD will cost more than one without.

Mike

 

[JBUDA54]

The lead was probably refering to a 18 pulse VFD vs a 6 pulse. The 18 pulse VFD would help with curbing harmonics. He was probably saying it was cheaper to put filters on a 6 pulse VFD rather than buying a 18 pulse VFD.

Maybe?

Jason

Jason Buda, PE
Greenville, SC
jbuda54@yahoo.com